A robot is a mechanical device which moves like a human being by making use of electrical and magnetic actions. The term “robot” is said to be derived from the Slavic word “ROBOTA” (slavish machine). In our country, the widespread use of robots began at the end of the 1960s, many of which were industrial robots, such as manipulators and conveyance robots, used, for example, for the purpose of achieving automatic industrial operations in factories without humans in attendance.
Installation-type robots, such as robots having arms, which are used by being implanted at a particular place, function only in fixed, limited working spaces for carrying out parts assembly/sorting or the like. In contrast, mobile robots can function in unlimited working spaces, so that they can freely move in predetermined paths or pathless areas in order to perform in place of human beings a predetermined or a desired human task, or to provide various wide-ranging services in place of living beings such as human beings or dogs. Of the mobile robots, legged mobile robots are unstable compared to crawler robots and robots with tires, so that it becomes difficult to control their posture and walking. However, legged mobile robots are excellent robots in that they can walk/run flexibly regardless of whether or not the ground is leveled, such as going up and down steps or a ladder or going over obstacles.
In recent years, advances have been made in the research and development of legged mobile robots such as humanoid robots which are designed using as a model the motion and mechanism of the body of an animal, such as a human being, which moves erect using two feet. There are increasing expectations for putting such robots into practical use. For example, Sony Corporation has presented a bipedal-walking humanoid robot “SDR-3X” on November 25.
Legged mobile robots may be used to help carry out or to carry out in place of human beings various difficult operations, such as in industrial tasks or production work. They carry out in place of human beings dangerous or difficult operations for human beings, such as maintenance work at nuclear power plants, thermal power plants, or petrochemical plants, parts transportation/assembly operations in manufacturing plants, cleaning in tall buildings, rescuing of people at places where there is a fire, etc.
Legged mobile robots may also be used for purposes closely related to life, such as for “living together” purposes or entertainment purposes, instead of helping human beings carry out a task. This type of robot imitates the way a living being fully shows its feelings and emotions using the four limbs or a movement mechanism of a legged walking animal which is relatively highly intelligent, such as a human being or a dog (pet). Legged mobile robots are required not only to faithfully execute a previously input behavior pattern, but also to respond vividly and dynamically to the words and behavior of, for example, a person (such as when praising, scolding, or hitting).
When legged mobile robots comprise, for example, uniform movable legs that are mounted to the left and right portions of the trunk, they can do the minimum work in the living space of human beings. In order for the legged mobile robots to function and behave in a more sophisticated manner, such as holding an object or handling a particular object in a working space, or making gestures or dancing using the upper half of the body, it is necessary to make the upper limbs move, and, desirably, to install an articulated bending mechanism for moving the finger tips even at the hands that are provided at the ends of the upper limbs.
A mechanism which can bend at a plurality of joints, such as the tail that many quadrupedal walking animals have, the neck of a giraffe, or the nose of an elephant, is very useful in making the robot imitate the way a living being shows its feelings and emotions.
However, in general, an articulated bending mechanism is designed and manufactured by disposing an actuator for every movable shaft. Therefore, for a member of a robot which is elongated like a finger and has very small intervals between links connecting each joint, the joint mechanism becomes large and complicated, so that the joint mechanism does not look like a finger.
An example of an elongated articulated mechanism is a bending mechanism used in, for example, an endoscope. However, this type of bending mechanism using a wire has difficulty generating a large driving force and is not suited for mass production because expensive structural members are used to assemble it.